Combined pneumatic-hydraulic press head with high actuation speed

Abstract

The combined pneumatic-hydraulic press head includes a body inside which a substantially cylindrical main chamber is defined; the chamber accommodates a main piston and a secondary piston so that they can slide along an axial direction. The main piston has a stem which protrudes from an axial end of the main chamber, and the secondary piston is spaced from the main piston on the side opposite to the stem. The two pistons sealingly divide the main chamber into three chambers: two end chambers, which can be connected to a source of compressed air or to the atmosphere in order to move the two pistons along the axis of the main chamber during the approach of the main stem or spacing motion with respect to the part to be treated, and an intermediate chamber which contains a liquid. An actuation stem is furthermore accommodated in the main chamber and sealingly passes through the secondary piston. A partition is arranged in the intermediate chamber, is rigidly fixed to the walls of the main chamber and is crossed by a passage for the actuation stem. The press is actuated by pushing the actuation stem through the passage toward the main piston so as to increase the pressure in the region of the intermediate chamber which is located between the main piston and the partition.

We claim: 
     
       1. Combined pneumatic-hydraulic press head comprising; a body (2, 33);   a main chamber (3, 36) defined in said body (2, 33) and having a main chamber axis (3a, 44), said main chamber (3, 36) having one end (6) and another end (12);   a main piston (4, 37) axially slideably accommodated inside said main chamber (3, 36) and having a stem (4a, 38), said stem (4a, 38) protruding from said one end (6);   a secondary piston (5, 43) located in said main chamber (3, 36) between said other end (12) and said main piston (4, 37);   a first end chamber (14, 39) defined between said main piston (4, 37) and said one end (6);   a second end chamber (15, 41) defined between said secondary piston (5, 43) and said other end (12);   an intermediate chamber (16) delimited by said main piston (4, 37) and said secondary piston (5, 43) and being filled with liquid;   first port means (17, 51) connected to said first end chamber (14, 39);   second port means (18, 45) connected to said second end chamber (15, 41) whereby pressurized fluid introduced therein acts directly on said secondary piston (5, 43), said first port means (17, 51) and said second port means (18, 45) being selectively connectable to a source of pressurized fluid and to the atmosphere for moving said secondary piston (5, 43), said liquid and said main piston (4, 37) along said main chamber (3, 36), whereby to rapidly move said stem (4a, 38) for positioning proximate to a workpiece (8);   a partition (20) provided in said intermediate chamber (16, 40) and having defined therein a passage (21, 42), and;   an actuation stem (19, 46) penetrating said second end chamber (15, 41), said secondary piston (5, 43) and said intermediate chamber (16, 40), said actuation stem (19, 46) being axially movable towards said passage (21, 42) with simultaneous return movement of said secondary piston (5, 43) to said other end (12) of said second end chamber (15, 41), said actuation stem (19, 46) being further axially movable into sliding sealing engagement with said passage (21, 42) for axially penetrating said intermediate chamber (16, 40) between said partition (20) and said main piston (4, 37), whereby to increase pressure in said liquid contained therein with corresponding actuation of said stem (4a, 38) for pressing a workpiece (8),   wherein said pneumatic-hydraulic press head further comprises valve means (30, 31) provided in said secondary piston (5).   
     
     
       2. Combined pneumatic-hydraulic press head according to claim 1, wherein said valve means (30, 31) include a valve needle (31), said valve needle (31) protruding from said secondary piston (5, 43), said valve means (30, 31) being openable upon contact of said valve needle (31) with said other end (12) of said main chamber (3, 36). 
     
     
       3. Combined pneumatic-hydraulic press head comprising; a body (2, 33);   a main chamber (3, 36) defined in said body (2, 33) and having a main chamber axis (3a, 44), said main chamber (3, 36) having one end (6) and another end (12);   a main piston (4, 37) axially slideably accommodated inside said main chamber (3, 36) and having a stem (4a, 38), said stem (4a, 38) protruding from said one end (6);   a secondary piston (5, 43) located in said main chamber (3, 36) between said other end (12) and said main piston (4, 37);   a first end chamber (14, 39) defined between said main piston (4, 37) and said one end (6);   a second end chamber (15, 41) defined between said secondary piston (5, 43) and said other end (12);   an intermediate chamber (16) delimited by said main piston (4, 37) and said secondary piston (5, 43) and being filled with liquid;   first port means (17, 51) connected to said first end chamber (14, 39);   second port means (18, 45) connected to said second end chamber (15, 41) whereby pressurized fluid introduced therein acts directly on said secondary piston (5, 43), said first port means (17, 51) and said second port means (18, 45) being selectively connectable to a source of pressurized fluid and to the atmosphere for moving said secondary piston (5, 43), said liquid and said main piston (4, 37) along said main chamber (3, 36), whereby to rapidly move said stem (4a, 38) for positioning proximate to a workpiece (8);   a partition (20) provided in said intermediate chamber (16, 40) and having defined therein a passage (21, 42);   an actuation stem (19, 46) penetrating said second end chamber (15, 41), said secondary piston (5, 43) and said intermediate chamber (16, 40), said actuation stem (19, 46) being axially movable towards said passage (21, 42) with simultaneous return movement of said secondary piston (5, 43) to said other end (12) of said second end chamber (15, 41), said actuation stem (19, 46) being further axially movable into sliding sealing engagement with said passage (21, 42) for axially penetrating said intermediate chamber (16, 40) between said partition (20) and said main piston (4, 37), whereby to increase pressure in said liquid contained therein with corresponding actuation of said stem (4a, 38) for pressing a workpiece (8);   an actuation chamber (23, 48) defined in said body (2, 33) coaxially to said second end chamber (15, 41), and;   an actuation piston (22, 47) slideably accommodated in said actuation chamber (23, 48) and being connected to said actuation stem (19, 46);   wherein said actuation chamber (23, 48) is sealingly separated from said second end chamber (15, 41) and has formed therein a first actuation port (24, 50) and a second actuation port (25, 49), said first actuation port (24, 50) being located between said actuation piston (22, 47) and an end of said actuation chamber (23, 48) proximate to said second end chamber (15, 41), said second actuation port (25, 49) being located between said actuation piston (22, 47) and an end of said actuation chamber (23, 48) remote from said second end chamber (15, 41), wherein said pneumatic-hydraulic press head further comprises valve means (30, 31) provided in said secondary piston (5).   
     
     
       4. Combined pneumatic-hydraulic press head according to claim 5, wherein said valve means (30, 31) include a valve needle (31), said valve needle (31) protruding from said secondary piston (5, 43), said valve mans (30, 31) being openable upon contact of said valve needle (31) with said other end (12) of said main chamber (3, 36). 
     
     
       5. Combined pneumatic-hydraulic press head comprising; a body (2, 33);   a main chamber (3, 36) defined in said body (2, 33) and having a main chamber axis (3a, 44), said main chamber (3, 36) having one end (6) and another end (12);   a main piston (4, 37) axially slideably accommodated inside said main chamber (3, 36) and having a stem (4a, 38), said stem (4a, 38) protruding from said one end (6);   a secondary piston (5, 43) located in said main chamber (3, 36) between said other end (12) and said main piston (4, 37);   a first end chamber (14, 39) defined between said main piston (4, 37) and said one end (6);   a second end chamber (15, 41) defined between said secondary piston (5, 43) and said other end (12);   an intermediate chamber (16) delimited by said main piston (4, 37) and said secondary piston (5, 43) and being filled with liquid;   first port means (17, 51) connected to said first end chamber (14, 39);   second port means (18, 45) connected to said second end chamber (15, 41) whereby pressurized fluid introduced therein acts directly on said secondary piston (5, 43), said first port means (17, 51) and said second port means (18, 45) being selectively connectable to a source of pressurized fluid and to the atmosphere for moving said secondary piston (5, 43), said liquid and said main piston (4, 37) along said main chamber (3, 36), whereby to rapidly move said stem (4a, 38) for positioning proximate to a workpiece (8);   a partition (20) provided in said intermediate chamber (16, 40) and having defined therein a passage (21, 42);   an actuation stem (19, 46) penetrating said second end chamber (15, 41), said secondary piston (5, 43) and said intermediate chamber (16, 40), said actuation stem (19, 46) being axially movable towards said passage (21, 42) with simultaneous return movement of said secondary piston (5, 43) to said other end (12) of said second end chamber (15, 41), said actuation stem (19, 46) being further axially movable into sliding sealing engagement with said passage (21, 42) for axially penetrating said intermediate chamber (16, 40) between said partition (20) and said main piston (4, 37), whereby to increase pressure in said liquid contained therein with corresponding actuation of said stem (4a, 38) for pressing a workpiece (8);   an actuation chamber (23, 48) defined in said body (2, 33) coaxially to said second end chamber (15, 41) and being sealingly separated from said second end chamber (15, 41);   an actuation piston (22, 47) slideably accommodated in said actuation chamber (23, 48) and being connected to said actuation stem (19, 46);   a first actuation port (24, 50) formed in said actuation chamber (23, 48) and being located between said actuation piston (22, 47) and an end of said actuation chamber (23, 48) proximate to said second end chamber (15, 41);   a second actuation port (25, 49) formed in said actuation chamber (23, 48) and being located between said actuation piston (22, 47) and an end of said actuation chamber (23, 48) remote from said second end chamber (15, 41), and;   valve means (30, 31) provided in said secondary piston (5), said valve means (30, 31) including a valve needle (31), said valve needle (31) protruding from said secondary piston (5, 43), said valve means (30, 31) being openable upon contact of said valve needle (31) with said other end (12) of said main chamber (3, 36).   
     
     
       6. Combined pneumatic-hydraulic press head according to claim 3, wherein said main chamber (3), said main piston (4), said stem (4a, 38), said secondary piston (5), said first end chamber (14), said second end chamber (15), said actuation stem (19), said passage (21) and said intermediate chamber (16) are axially aligned with said main chamber axis (3a). 
     
     
       7. Combined pneumatic-hydraulic press head according to claim 3, wherein said main chamber (3, 36), said main piston (37), said stem (38) and said first end chamber (39) are coaxial with said main chamber axis (44), and wherein said secondary piston (43), said actuation stem (46), said passage (42) and said second end chamber (41) are transverse to said main chamber axis (44).   
     
     
       8. Combined pneumatic-hydraulic press head according to claim 6, wherein said main piston (4) has formed therein a depression (26), said depression (26) facing said actuation stem (19), said actuation stem (19) being partially accommodatable in said depression (26) of said main piston (4).